Tunable devices can be used for various applications such as performing signal processing operations and functions. It is advantageous to have tunable devices because one can tune and/or calibrate a device to account for any manufacturing glitches while implementing a design on a chip or to provide a user the flexibility to adjust, if desired, the operating conditions of a device. For example, a filter can be tuned to adjust the pass band spectral range. In another example, an amplifier can be tuned for achieving a particular gain.
One method of tuning devices is by tuning the capacitance. For example, basic designs of filters include LR (inductor-resistor) and RC (resistor-capacitor) filters, and by tuning the capacitance, one can tune the filter. A tunable capacitance is also useful in several other devices such as charge capacitors, tunable antennas, and mobile phones.
Several methods currently exist for tuning capacitors. However many of the methods require excessive circuit size, complex circuitry, and/or result in increased loss, and low Q-factors. Furthermore, tradeoffs between capacitance tuning, impedance matching, and a high Q factor make designs for tunable capacitive designs complicated.